Objective    To explore the radiological manifestations of viral encephalitides by magnetic resonance imaging (MRI)

diffusion weighted imaging (DWI) and

1

H magnetic resonance spectroscop

y (

1

H-MRS).     Methods    The conventional MR imaging

DWI and multivoxel 2D

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H-MRS were performed in 36 cases with acute or subacute viral encephalitis. The data by DWI and

1

H-MRS were calculated and analyzed

and statistical analyses were performed by using the software of SAS 8.2.     Results    Viral encephalitis presented as single (14 cases) or multiple lesions (22 cases)

located mainly in cortices

subcortical and periventricular white matter

basal ganglia and thalami. The lesions carried slightly long T

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and long T

2

intensity with faint patch shape enhancement on contrast-enhanced image. Abnormalities were found on DWI

including isointensity or slightly hyperintensity in 11 cases

homogeneous hyperintensity in 4 cases

and inhomogeneous hyperintensity in 21 cases. On apparent diffuse coefficient (ADC) map

increased diffusivity of the lesion were demonstrated in 26 cases

and increased and restricted diffusivity were seen in the other 10 cases. The mean ADC value of viral encephalitis was significantly higher than that of normal control tissues [(0.93±0.29)×10

-3

and (0.76±0.32)×10

-3

mm

3

s

P

=0.007

]

. On

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H-MRS

choline (Cho)

creatin (Cr) and n-acetyl aspartate (NAA) of viral encephalitis were significantly lower than those of normal control tissues [Cho (364.3±56.3)

vs

(440.2±52.8)

P

<

0.01; Cr (178.4±28.2)

vs

(269.3±37.5)

P

<

0.05; NAA (203.7±33.8)

vs

(386.5±68.5)

P

<

0.01

]

. Lactate peak was found in 3 cases.     Conclusion    DWI and

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H-MRS present the information for the histological and metabolism feature of viral encephalitis

and should be applied as an important supplemental examination besides conventional MRI.